Rescue workers were digging through rubble Thursday for any additional victims who may have been trapped when a building under demolition collapsed onto a neighboring thrift store, killing six people and injuring 14, including one who was pulled from the debris nearly 13 hours later.

Workers were using buckets and their bare hands to move bricks and rubble in a search-and-rescue operation with no end immediately in sight.

“We’re going to keep searching until we’re absolutely sure no one else is there,” battalion fire chief Charles Lupre said shortly before dawn. He said there were no reports of anyone missing, but there was always the chance that someone was inside who wasn’t reported missing.

It was unclear what role the demolition work might have played in the collapse, but the accident raised questions about how closely the highly visible spot on Market Street, one of Philadelphia’s signature boulevards, was being monitored, particularly amid word of the demolition contractor’s many legal and financial troubles. Officials from the U.S. Department of Labor and Occupational Safety and Health Administration were at the scene.

For weeks, people working nearby had watched with growing concern as a crew took down the vacant four-story building next to a Salvation Army thrift store at the edge of downtown.

A roofer atop another building didn’t think the operation looked safe. A pair of window washers across the street spotted an unbraced, 30-foot section of wall and predicted among themselves the whole building would simply fall down.

On Wednesday, that’s what happened. The unstable shell of a building collapsed into a massive heap of bricks and splintered wood, taking part of the thrift store with it.